The official answer from the glass manufacturers is, All tested compatible glasses have been tested by the FDA for food bearing surfaces and were determined to be suitable.However, if you add other processes or compounds to the items, for example paint, stains, decals, glazes, etc. it is important to check that these items are also approved for food bearing surfaces. In addition it is of the utmost importance that dinnerware items be properly annealed, especially if youre going to place hot food on them - the thermal shock could cause a break in poorly annealed items.
This Randys ProTip brought to you from the book Introduction to Glass Fusing by Petra Kaiser. VisitWardell Publications.
Also, at Delphi we take food safety and dinnerware very seriously. We always recommend that certain glasses are capped with clear. These are usually irids, dichro and glass with texture, since these can also trap food particles. Please see this Bullseye link for more information: http://www.bullseyeglass.com/products/faq/#faq_011